Charging from TV

JeffroNC

I found this kind of by accident. I know I don't get very much current through the 7 way connector on my F150. I am putting the smaller version of this on my future mod list.
https://www.adventurousway.com/blog/rv-electrical-upgrade-part-3-dc-charger-truck-12v-socket

Cbusguy

excellent link.    Just the info I was looking for.

thx

BrianZ

Interesting article that sounds like a good solution for those with a high-amp alternator in their TV plus a ton of Amp-Hours invested in a lithium battery bank that can recharge at high current rates. 
Seems like overkill for most T@B users, but I can see the utility for dry camping for extended periods with limited solar when combined with fairly long drives inbetween stays.

Cbusguy

@BrianZ this should fit my situation.....this would work great for my road runs from home to destination.   I have installed a 250 amp alternator in my truck from powerbastards.com and intend on having 500 Ahr of lithium for running the ac while rest area, walmart,  parking lot surfing to my destination. 

but with the removal of the danby ac unit and addition of the cool cat that might change.     

BrianZ

Good point, @Cbusguy, I had forgotten about the power hungry A/C unit, or for that matter being able to run a 3-way frig on DC without worrying about killing the TV battery.  I guess most have learned to accept the T@B's built-in limitations when it comes to power, or to mitigate them with solar, etc, but if you can afford it, this could be closer to an ideal solution.  I noticed the DC-DC charger accepts solar input, which makes it more flexible when not on the road.  I wonder what 500AH of lithium batteries costs, about $5K?  And what is the estimated lifespan?

RollingBnB

JeffroNC said:

I found this kind of by accident. I know I don't get very much current through the 7 way connector on my F150. I am putting the smaller version of this on my future mod list.
https://www.adventurousway.com/blog/rv-electrical-upgrade-part-3-dc-charger-truck-12v-socket

On most tv, if you turn on the headlights it will override the battery full reduced output and keep the alternator at full power.

Cbusguy

@BrianZ  I was looking at prismatic cells opposed to battleborn, renology, victron or aims.       I can get about 500 amp hours in prismatic cells for in the $2k range, shipping can cost as much as the battery,   or even a used tesla battery pack which is 24 volts and 250 amp hours for about $1.2k tested from a reputable seller.    

Life expectancy on lithium is too variable to gauge......You could destroy your pack in one trip by completely discharging it or overcharging it.     most of the research I have seen says that an 80% of max charge down to 20% capacity will yield about 10,000 charge cycles........and a 90% to 10% will yield about 7500 cycles.....   in my book that is a life time of use in an rv.....   Compare that with several hundred cycles in a lead acid or agm,    makes sense.    But it is that huge up front cost and some engineering on the end users part.

I like the cool cat,  removing the window ac and the air water leak from the side of the trailer makes a bunch of sense in my book,    just makes it tougher to run it off grid on battery.   I was sitting here crunching the numbers and it ain't pretty

the specs are tough to get a true read on.....Though travels with delaney runs his on a 2k generator if memory serves,  not sure if he installed a soft start or not.......     you have lock amperages that exceed 60 amps.....so guessing it surges to 50 amps to start.      with a running amperage of 12-15 amps.    just guessing.   which means we are looking at 100-150 amps in the 12 volt world to run it......and assuming a 6 hour over night that puts it in the 600 to 900 amp hour range of needs.....add 20 percent for margin of safety and losses to inefficiencies in hardware you are in the 1000 amp hour range.      Just no longer practical in my book.   

then you need to recharge that battery some how......even with a 100 amp charge current you are looking at 10 hours......that is a huge amount of power and getting into a range I am no longer comfortable dealing with.   at that current you are approaching max c rating of the battery and could damage it.....

my head is spinning now.......too many variables.

I will just wait till it is in the driveway and put it on my amp probe and see what the real numbers are.

JeffroNC

@RollingBnB interesting point. I need to get my monitor installed to see. Although the wire gauge to the trailer plug is another limiting factor which the author corrected.

klenger

^^  Agreed about the wire gauge.  A clever but probably effective way to charge the T@B battery from the tow vehicle would be to connect a 1000 watt inverter directly to the tow vehicle electrical system to ensure minimum voltage drop from the alternator to the inverter.  Then, simply plug the 120 vac campground power connector to the inverter 120 vac output.  Upgrading the T@B converter and wiring would further help.

Cbusguy

@klenger even with that sort of an inverter setup it is recommended 2/0 gauge wire.    All though you could use the inverter as your current limiter and down size it.   My guess would be that it would have a very short life span as it would run at 100% capacity most of the time.   

There are a number of off grid types that do exactly what your are talking about to increase the charge current from their generators.....the honda only allows for 10 amps at 12 volts,   They run an ac charger from the generator and can get 50 amps at 12 volts.     

But ya know,   good enough is good enough, sometimes....

BrianZ

I was also intrigued by this comment in the referenced article:

"I actually connected to the OBD-II port on the truck and monitored the PID corresponding to available current from the alternator - even when sitting at idle, there's at least 80 Amps of capacity available."

I'm curious which PID code he is referring to, as I have only seen one for voltage in my bluetooth OBD2 reader app, nothing for current.  Guessing it's one that is unique to Ford, as I've read they have many more than the standard ones or other manufacturers.

I have only used my OBD2 device for monitoring transmission temps while towing, and even that required some research & setting up a custom PID code & formula to work for our model year.  I guess I can always just look at our Victron battery monitor to see charging current at the battery.

Tundra57

I installed a renogy dc to dc converter in my tab 400. This provides the correct charging cycle for the tab battery at the expense of more current from the TV. I also ran a seperate feed from the battery to deal with voltage drop in the tv trailer plug wiring. Before this mod, my three way fridge would deplete my tab battery down to 50% on a long run with some night travel. Now its fine. Definately a worthwhile upgrade. It also isolates the tv battery from the tab so the tab can't discharge the tv battery if you forget to unplug.

AirBoss

Its charged...or its not. If its charged, cool. If its not, charge it. If it won't hold a charge, buy a new one...done. 

TNOutback

Thanks for the article; especially since I have the exact same truck as the author.  I am lost though on his comment about the blue wire on the DC-DC charger.  What does he mean to “pull it high”?

Sprockethead

I live in an Association, so, I am not allowed to Park in my Driveway!... Charging my battery is a challenge. To solve this problem, I just ordered the Renogy DC-DC charger to install in my 4Runner and some 8 gage wire for a "charging cord". I chose the 20 amp, so I don't Overload my stock alternator. I use about 25 amps/day. After a 3-4 day weekend and 4 hour drive, the Renogy and my Solar should charge the battery on my way back to Storage

https://www.amazon.com/gp/product/B07Q5VYPCF/ref=ppx_yo_dt_b_asin_title_o02_s01?ie=UTF8&psc=1